Do you have rear climate control in your minivan or SUV? If so, you may have a second AC unit or booster in your vehicle. Some only control the fan but others have a second air conditioning unit for the rear. When you use the separate rear one, it KILLS your fuel economy. See if it makes a difference for you, you'll know right away.
To get around this, we sometimes just use the main AC, but boost up the fan and direct it to the rear.
by gory on July 21 2010
this tip works for 52% of voting Fuelly members.